Electric pump

ABSTRACT

An electric pump includes: a motor housing; a pump housing adjacent to the motor housing; a rotor accommodated in the motor housing and axially supported by a rotating shaft; a stator disposed radially outward of the rotor and fixed to the motor housing; a pump unit accommodated in the pump housing and configured to suck and discharge a fluid by rotation of the rotor; and a cup-shaped can provided between the rotor and the stator to prevent the fluid in the pump unit from being introduced into the stator. A seal member is disposed between the can and the motor housing, and a communication path communicating inner and outer sides of the can is formed between the motor and pump housings at a position closer to an opening side of the can than the seal member.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is based on and claims priority under 35 U.S.C. § 119 to Japanese Patent Application 2018-096552, filed on May 18, 2018, the entire contents of which are incorporated herein by reference.

TECHNICAL FIELD

This disclosure relates to an electric pump.

BACKGROUND DISCUSSION

An electric pump is used, for example, to supply hydraulic oil to a hydraulic device such as a transmission mounted on a vehicle. In such an electric pump, in order to increase the efficiency of cooling of a motor unit, a part of the hydraulic oil discharged from the electric pump may be circulated through a rotor of the motor unit. However, when the hydraulic oil is introduced into a stator of the motor unit, the operation of the motor unit may be hindered. Therefore, in order to prevent the hydraulic oil from being introduced into the stator, a can is disposed between the stator and the rotor supported on a rotating shaft in the motor unit (e.g., JP 2015-218650 A (Reference 1)).

An electric pump may have a higher motor efficiency as the distance between a stator and a rotor is smaller. Therefore, a can disposed between the stator and the rotor may have a thickness as small as possible. The inside of the can is configured as a hermetically sealed space that is shut off from the outside other than a pump unit such that hydraulic oil introduced into the rotor is not discharged toward the stator. Therefore, when the hydraulic oil is introduced to the inside of the can from the pump unit, the hydraulic pressure inside the can is increased. In a case where the can is configured to have a small thickness, the can may be deformed under the influence of an increase in the hydraulic pressure inside the can. In addition, and the can may be damaged due to an increase in the deformation amount. Then, the function of a motor unit is greatly impaired in the electric pump.

Thus, a need exists for an electric pump which is not susceptible to the drawback mentioned above.

SUMMARY

A feature of electric pump according to an aspect of this disclosure resides in that the electric pump includes a motor housing, a pump housing adjacent to the motor housing, a rotor accommodated in the motor housing and axially supported by a rotating shaft, a stator disposed radially outward of the rotor and fixed to the motor housing, a pump unit accommodated in the pump housing and configured to suck and discharge a fluid by rotation of the rotor, and a cup-shaped can provided between the rotor and the stator to prevent the fluid in the pump unit from being introduced into the stator, in which a seal member is disposed between the can and the motor housing, and a communication path that communicates an inner side of the can with an outer side of the can is formed between the motor housing and the pump housing at a position closer to an opening side of the can than the seal member.

With this configuration, the fluid in the pump unit is prevented from being introduced into the stator by the can and the seal member disposed between the can and the motor housing even when the fluid in the pump unit is introduced into the rotor of a motor unit. Here, in the motor unit, when the fluid is introduced to the inside (the rotor) of the can, a fluid pressure may be increased due to an increase in the amount of the fluid inside the can. Thus, in this configuration, the communication path is formed at the opening side of the can to communicate the inner side of the can with the outer side of the can. By the communication path, the fluid introduced to the inside of the can may be easily discharged to the outside of the can. Thus, since an increase in the fluid pressure is prevented even when the fluid is introduced to the inside of the can, it is possible to effectively prevent deformation of the can even when the thickness of the can is small. As a result, the electric pump may increase the motor efficiency by reducing the thickness of the can.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and additional features and characteristics of this disclosure will become more apparent from the following detailed description considered with the reference to the accompanying drawings, wherein:

FIG. 1 is a cross-sectional view of an electric pump disclosed here;

FIG. 2 is a cross-sectional view of a major part of the electric pump;

FIG. 3 is a cross-sectional view of a major part of the electric pump;

FIG. 4 is a perspective view of a can; and

FIG. 5 is a cross-sectional view of a major part of an electric pump according to another embodiment.

DETAILED DESCRIPTION

Hereinafter, an embodiment disclosed here will be described with reference to the accompanying drawings.

As illustrated in FIG. 1, an electric pump 1 includes a pump unit 10, a motor unit 30, and a driver unit 50. The electric pump 1 is used as, for example, an oil pump that supplies hydraulic oil to a transmission of a vehicle. In addition, the electric pump 1 may be used for the supply of a fluid other than the hydraulic oil.

The pump unit 10 includes a pump housing 12 having a circular accommodating recess 18 formed in one end surface thereof and a pump cover 11 that covers the end surface of the pump housing 12 in which the accommodating recess 18 is formed. Both the pump housing 12 and the pump cover 11 are formed of an aluminum alloy. A bearing bore 19 which is eccentric from the center of the accommodating recess 18 is formed in the pump housing 12. A rotating shaft 15 is inserted into the bearing bore 19, so that the rotating shaft 15 is rotatably supported by the bearing bore 19.

A pump 14 provided in the accommodating recess 18 includes an inner rotor 22 forming outer teeth and an outer rotor 23 forming inner teeth, which are engaged with each other. The outer peripheral surface of the outer rotor 23 is supported in the accommodating recess 18 so as to be rotatable. The inner rotor 22 is press-fitted and fixed to one end portion of the rotating shaft 15 so as to be coaxial with the rotating shaft 15. The other end portion of the rotating shaft 15 opposite to the side to which the inner rotor 22 is fixed protrudes from the pump housing 12 toward the motor unit 30.

A pump chamber 24, the volume of which increases or decreases according to rotation, is formed between the teeth of the inner rotor 22 and the outer rotor 23 which are engaged with each other. The pump cover 11 is formed therethrough with a discharge path 25, through which hydraulic oil in the pump chamber 24 is discharged, and a suction path 26, through which the hydraulic oil is sucked.

The motor unit 30 includes an annular stator 33 and a cylindrical rotor 34 which are accommodated in a motor housing 32, the rotor 34 being located radially inward with a predetermined distance from the inner peripheral surface of the stator 33. The rotor 34 is axially supported on the rotating shaft 15. The motor housing 32 is provided adjacent to the pump housing 12. Both the stator 33 and the rotor 34 are coaxial with the axis of the rotating shaft 15. The rotor 34 includes a rotor core 35 formed by laminating thin electromagnetic steel plates and permanent magnets 36 accommodated in a plurality of slots formed in the rotor core 35. The rotor 34 is provided radially inward of the stator 33 so as to face the stator 33 fixed to the motor housing 32.

The stator 33 includes a stator core 39 formed by laminating electromagnetic steel plates and a coil 40 wound around a coil support frame 41 which is formed of an insulator. A cylindrical space 37 is formed between the inner peripheral side of the stator 33 and the rotor 34.

The driver unit 50 is provided at one side of the motor unit 30 opposite to the pump unit 10. The driver unit 50 is configured by disposing a printed board 53, on which an electronic component is mounted, in a driver accommodating portion 52 which is formed by combining the motor housing 32 and a cover part 51 with each other. The driver unit 50 generates an alternating magnetic field by energizing the coil 40 of the stator 33 to rotate the rotor 34. The inner rotor 22 is rotated via the rotating shaft 15 by the rotation of the rotor 34, and the outer rotor 23 is rotated according to the rotation of the inner rotor 22. Thus, the hydraulic oil circulating through the suction path 26 is sucked to the pump chamber 24 and is discharged from the discharge path 25.

A cup-shaped (bottomed cylindrical) can 60 illustrated in FIG. 4 is disposed in the cylindrical space 37 of the rotor 34. The can 60 is formed of a plate material such as a nonmagnetic material (e.g., stainless steel), and formed in a bottomed cylindrical shape. The can 60 has an outer circumferential diameter substantially the same as the inner diameter of the cylindrical space 37, and the side surface of the can 60 is provided between the stator 33 and the rotor 34. That is, the rotor 34 is accommodated inside the can 60. The can 60 has an opening 61 at the side of the pump unit 10 and has a flange 62 at the side of the opening 61. The flange 62 extends radially outward between the motor housing 32 and the pump housing 12. A seal member 65 is disposed between the flange 62 and an end surface 42 of the motor housing 32 at the side of the pump unit 10. The seal member 65 is configured with an elastically deformable O-ring, for example, and a portion of the seal member 65 is accommodated in a circular groove 43 formed in the end surface 42. A gap 73 is formed between the flange 62 of the can 60 and the end surface 42 which faces the flange 62. The can 60 is held with the flange 62 and pressed against an end surface 27 of the pump housing 12 at the side of the motor unit 30 by an elastic force of the seal member 65 in a state where the flange 62 abuts on the seal member 65 (see FIG. 2).

When the pump 14 rotates and the hydraulic oil is sucked to the pump chamber 24, a part of the hydraulic oil in the pump chamber 24 circulates through a gap between the bearing bore 19 and the rotating shaft 15 and is introduced to the inside of the can 60. When the amount of the hydraulic oil introduced to the inside of the can 60 is small and the hydraulic pressure inside the can 60 is in a low pressure state, as illustrated in FIG. 2, the flange 62 of the can 60 is pressed against the end surface 27 of the pump housing 12 at the side of the motor unit 30 by the seal member 65. Thus, the inside of the can 60 is kept in a hermetically closed state with respect to the outside other than the pump unit 10.

Meanwhile, when the hydraulic oil is introduced to the inside of the can 60 and the hydraulic pressure inside the can 60 is increased to a high pressure state during an operation of the electric pump 1, as illustrated in FIG. 3, the hydraulic pressure of the hydraulic oil acts on the flange 62, and the flange 62 pushes up the seal member 65 toward the end surface 42 of the motor housing 32. At this time, the seal member 65 is compressed and elastically deformed, and the flange 62 approaches the end surface 42 of the motor housing 32. That is, the gap 73 between the flange 62 and the end surface 42 of the motor housing 32 is reduced, and a communication gap 70 (an example of a communication path) is formed between the flange 62 and the end surface 27 of the pump housing 12 to communicate the inner side of the can 60 (the side on which the rotor 34 is accommodated) with the outer side of the can 60. In this way, the communication gap 70 is formed as a communication path between the flange 62 and the end surface 27 of the pump housing 12 at the side of the motor unit 30. Thus, since the hydraulic oil is discharged from the communication gap 70 toward the outer side of the can 60 even when the hydraulic oil is introduced into the can 60 and comes into a high pressure state, a further increase in the hydraulic pressure inside the can 60 is prevented. As a result, it is possible to effectively prevent deformation of the can 60 even when the can 60 has a small thickness shape.

As illustrated in FIGS. 2 and 3, the motor housing 32 and the pump housing 12 are fastened and fixed to each other by a bolt 81 in a state where a gap 72 is formed between the end surface 42 and the end surface 27 by a collar 80 which is thicker than the thickness of the motor housing 32. Thus, the hydraulic oil inside the can 60 which has circulated through the communication gap 70 and has reached the outside of the can 60 further circulates through the gap 72 and is discharged to the outside of the electric pump 1. Even when the hydraulic oil is discharged to the outside of the pump 1, in a case where the electric pump 1 is disposed, for example, in an oil tank, there is no problem since the hydraulic oil discharged to the outside of the electric pump 1 is discharged to the oil tank. When the electric pump 1 is provided outside the oil tank, for example, the electric pump 1 may be configured to return the hydraulic oil discharged to the outside of the electric pump 1 to an oil pan (not illustrated) or the suction path 26 through an oil path (not illustrated).

In a state illustrated in FIG. 2, when the length of the seal member 65 in a direction perpendicular to the flange 62 is defined as a height H and the magnitude of the gap 73 between the end surface 42 of the motor housing 32 and the flange 62 of the can 60 is defined as a width T, the width T is set with respect to the height H such that the “width T/height H” ranges from 5% to 50%. When the “width T/height H” is less than 5%, the gap 73 is too small, and a sufficient magnitude of the communication gap 70 may not be secured even when the gap 73 is small, so that the hydraulic oil may not be appropriately discharged from the inside of the can 60. Meanwhile, when the “width T/height H” exceeds 50%, the seal member 65 may easily protrude from the groove 43 in the end surface 42, and there is a possibility of the sealing function of the seal member 65 being impaired.

Second Embodiment

As illustrated in FIG. 5, in a second embodiment, a groove 28 is formed in the end surface 27 of the pump housing 12 along a direction in which the flange 62 extends, and the groove 28 forms a communication path 71 that communicates the inner side of the can 60 with the outer side of the can 60. The communication path 71 communicates with the gap 72 formed between the end surface 42 of the motor housing 32 and the end surface 27 of the pump housing 12. The inner side of the can 60 and the outer side of the can 60 are always in communication with each other by the communication path 71 regardless of the hydraulic pressure inside the can 60. Thus, the hydraulic oil introduced into the can 60 may be discharged to the outside of the electric pump 1 through the communication path 71 and the gap 72. The communication path 71 (the groove 28) may be formed in a singular or in a plural number.

In the present embodiment, even when the amount of hydraulic oil introduced into the can 60 is small and the hydraulic pressure is in a low pressure state, the hydraulic oil may be discharged to the outside of the can 60 by the communication path 71. Therefore, since the hydraulic oil is discharged from the communication path 71, an increase in hydraulic pressure is prevented. Therefore, the inside of the can 60 may be kept in a low pressure state even when the amount of introduction of the hydraulic oil is increased. Thus, it is possible to effectively prevent deformation of the can 60 even when the thickness of the can 60 is small compared to a first embodiment. As a result, the electric pump 1 may increase the motor efficiency by reducing the thickness of the can 60.

In addition, in the present embodiment, since the inner side and the outer side of the can 60 are always in communication with each other due to the presence of the communication path 71, there is a possibility of the invasion of foreign substances or the introduction of air from the outside of the electric pump 1 through the communication path 71. Therefore, the depth of the communication path 71 (the groove 28) may be as small as possible in order to prevent the invasion of foreign substances and the introduction of air as much as possible. In addition, in order to prevent the invasion of foreign substances from the outside of the electric pump 1, a filter for collecting foreign substances may be disposed at a predetermined position of a passage that is continuous to the communication path 71 of the electric pump 1.

Other Embodiments

(1) Although the second embodiment has described an example in which the groove 28 is formed in the end surface 27 of the pump housing 12 in order to form the communication path 71, a groove may be formed in the flange 62 of the can 60 to form the communication path 71, or grooves may be formed in both the end surface 27 and the flange 62 to form the communication path 71.

(2) Although the embodiment has described an exemplary shape in which the can 60 has the flange 62, the can 60 may be configured without the flange 62. In this case, a communication path is formed between at least a portion of the end of the opening 61 in the can 60 and the end surface 27 of the pump housing 12 to communicate the inner side of the can 60 with the outer side of the can 60. The communication path may be formed by providing, for example, a notch in the end of the opening 61 in the can 60, or may be formed by providing a groove in the end surface 27 of the pump housing 12. In addition, the communication path may be formed by both the notch in the can 60 and the groove in the end surface 27 of the pump housing 12.

(3) A groove may be formed in one or both of the end surfaces 42 and 27 which face each other between the motor housing 32 and the pump housing 12 so that the communication path communicates with the outside of the electric pump 1. In this case, the gap 72 is unnecessary.

This disclosure may be widely used for an electric pump having a can.

Another feature resides in that the can includes a flange that is provided on an end thereof at the opening side and extends radially outward between the motor housing and the pump housing, the seal member is elastically deformable and is disposed between the motor housing and the flange, and the flange of the can is configured to abut on the seal member in a state of having a gap with the motor housing, and the communication path is formed by narrowing the gap.

With this configuration, the flange of the can abuts on the seal member and is spaced apart from the motor housing. Here, when the fluid pressure is increased due to an increase in the amount of the fluid inside the can, the fluid pressure acts on the flange of the can so that the flange presses the seal member. At this time, as the seal member is elastically deformed, the flange approaches the motor housing. That is, the gap between the flange and the motor housing is reduced, and a communication path is formed between the flange and an end surface of the pump housing to communicate the inside of the can with the outside of the can. Thus, since the fluid may be discharged from the communication path even when the fluid is introduced to the inside of the can, the fluid pressure inside the can is prevented from being increased. As a result, it is possible to effectively prevent deformation of the can even when the can has a small thickness shape.

In addition, since the can is disposed in a state where the flange abuts on the end surface of the pump housing, the inside of the can may be configured as a hermetically sealed space. With the configuration described above, it is possible to prevent foreign substances from being introduced to the inside of the can from the outside.

Another feature resides in that the can includes a flange that is provided on an end thereof at the opening side and extends radially outward between the motor housing and the pump housing, the seal member is elastically deformable and is disposed between the motor housing and the flange, and the flange of the can is pressed by the seal member to close the communication path.

With this configuration, the flange is pressed by an elastic force of the seal member to close the communication path. Here, when the fluid pressure inside the can is not too high to deform the cap (in a case of a low fluid pressure), the communication path may be kept closed. That is, the reduction of the fluid may be minimized so as not to discharge more fluid to the outside of the can than necessary.

The principles, preferred embodiment and mode of operation of the present invention have been described in the foregoing specification. However, the invention which is intended to be protected is not to be construed as limited to the particular embodiments disclosed. Further, the embodiments described herein are to be regarded as illustrative rather than restrictive. Variations and changes may be made by others, and equivalents employed, without departing from the spirit of the present invention. Accordingly, it is expressly intended that all such variations, changes and equivalents which fall within the spirit and scope of the present invention as defined in the claims, be embraced thereby. 

What is claimed is:
 1. An electric pump comprising: a motor housing; a pump housing adjacent to the motor housing; a rotor accommodated in the motor housing and axially supported by a rotating shaft; a stator disposed radially outward of the rotor and fixed to the motor housing; a pump unit accommodated in the pump housing and configured to suck and discharge a fluid by rotation of the rotor; and a cup-shaped can provided between the rotor and the stator to prevent the fluid in the pump unit from being introduced into the stator, wherein a seal member is disposed between the can and the motor housing, and a communication path that communicates an inner side of the can with an outer side of the can is formed between the motor housing and the pump housing at a position closer to an opening side of the can than the seal member.
 2. The electric pump according to claim 1, wherein the can includes a flange that is provided on an end thereof at the opening side and extends radially outward between the motor housing and the pump housing, the seal member is elastically deformable and is disposed between the motor housing and the flange, and the flange of the can is configured to abut on the seal member in a state of having a gap with the motor housing, and the communication path is formed by narrowing the gap.
 3. The electric pump according to claim 1, wherein the can includes a flange that is provided on an end thereof at the opening side and extends radially outward between the motor housing and the pump housing, the seal member is elastically deformable and is disposed between the motor housing and the flange, and the flange of the can is pressed by the seal member to close the communication path. 